Skin pass mills and methods of rolling



March 13, 1962 T. A. FOX 3,024,679

SKIN PASS MILLS AND METHOD OF ROLLING Filed July 1, 1957 3 Shets-Sheet 1m Fig.l.

f I v Q -d -l Q ----3'/ n 37' v [,1 r) 7 I INVENTOR Thomas A. Fox

3 1 WWW March 13, 1962 T. A. FOX 3,024,679

SKIN PASS MILLS AND METHOD OF ROLLING Filed July 1, 1957 3 Sheets-$heet2 Fl 9 .5. l 'T |O2b I020 I03b I030 Ill H0 I07b l07a Fl 9 6 A.

No Roll-Bending Pressure Applied.

. II 0'00 Tatal Gage Vanahon 0.0005

Edge Center Edge Fl 9 Roll-Bending Pressure 650 PSI.

+0.00I I Total Gage Variation 0.000l5 Edge Center Edge INVENTOR Q ThomasA. Fox fiw w March 13, 1962 T. A. FOX 3,024,679

SKIN PASS MILLS AND METHOD OF ROLLING Filed July 1, 1957 3 Sheets-Sheet3 lNVENTOR Thom as A. Fox

WUZ-M/Y 3,024,679 Patented Mar. 13, 1962 3,024,679 SKIN PASS MILLS ANDMETHGDS F RGLHNG Thomas A. Fox, 2011 Wingate Road, Youngstown, GhioFiled Italy 1, 1957, Ser. No. 668,)89

4 Claims. (Cl. 89-56) This invention relates to skin pass mills andparticularly to a skin pass mill capable of maintaining substantiallyconstant pass pressure on a strip regardless of variations in stripthickness. It has long been the practice in strip rolling to pass thestrip after reductions through a skin pass or temper mill in order toimpart a desired surface finish to the product, to produce uni-formflatness and to develop desired mechanical properties. The object is toflatten the strip and to impart the proper surface in a single passwhile imparting a desired hardness to the strip. Conventionally, skinpassing has been done on 4-high single stand temper mills, althoughtemper rolling or skin rolling has more recently been to an increasingextent, done on Z-high stand tandem temper mills by careful control andhandling of the mills. Difficulty has, however, been experienced inmaintaining uniformity over the entire surface of the temper rollproduct because of variations in the strip thickness fed to the millregardless of whether a 4-high mill or a 2- high mill is used for thetemper pass.

I have found that these problems of nonuniformity can be solved byproviding a skin pass mill of particular structure and by followingcertain method steps.

I provide a mill having a housing, a pair of work rolls mounted in thehousing for rotation and adapted to receive the strip to be temperrolled between them, yieldable means acting on at least one of the rollsurging said one roll toward the other under substantially constantpressure. Preferably the yieldable means is a hydraulic cylinderactuated by a source of hydraulic fluid under constant pressure andmeans delivering said fluid to the hydraulic cylinder whereby the rollsare urged together under constant pressure. It is also desirable thatthere be provided flow control means to assure substantially identicalvolumes of hydraulic fluid to each cylinder. The yieldable meanspreferably works on the lowermost roll of the pair. The work rolls maybe backed up by back-up rolls and the pressure applied to the lowermostback-up roll. I have found that more uniform temper passing can beobtained over the entire width of the mill by applying hydraulicpressure in both directions to the working rolls when the rolls are usedwith crowned backup rolls. In this way, the work rolls can be induced totake a desired crown to follow the surface of the strip so that uniformwork is applied to the entire surface of the strip.

I have found that with this apparatus 1 can use much smaller work rollsthan are normally used in skin passing and can thereby produce the sameeffects with less reduc ion of the strip than can be done withconventional mills. I have also found that a more uniform surfacehardening can be achieved with my apparatus and method than withconventional mills. For example, I have found that strip which byordinary skin pass methods would have a to 14 point edge to edgedifferential in rockwell hardness will have only a 3 to 5 point edge toedge differential when rolled by the method and apparatus of the presentinvention. Moreover, the method of rolling will produce unique products.For example, a normalized strip can be skin passed by my method toproduce a uniform hardened surface from edge to edge.

While I have set out certain objects, advantages and purposes of thisinvention in the foregoing general description, other advantages,purposes and objects will be apparent from the following description andthe accompanying drawings in which:

United States Patent Gfifice FIGURE 1 is a side elevation of a skin passmill according to this invention;

FIGURE 2 is a side elevation of a second embodiment of skin pass millaccording to this invention;

FIGURE 3 is a diagrammatic view of a preferred embodiment of controlcircuit and hydraulic cylinder for actuating the rolls in the skin passmill of my invention; and

FEGURE 4 is a third embodiment of my invention in cluding means forimparting crown to the work rolls.

FIGURE 5 is a schematic front elevation, showing work rolls inexaggerated contour, illustrating the general arrangement of a millaccording to one form or" my invention;

FIGURES 6A and 6B illustrate schematically the results to be obtained onstrip rolled in a mill as illustrated in FIGURE 5.

Referring to the drawings, I have illustrated a roll housing ltlcarrying work rolls 11 and 12 backed up by back-up rolls 13 and 14. Thework rolls 11 and 12 are mounted on opposite sides of a strip pass line15. The uppermost work roll 11 is backed up by an upper backup roll l3and each of the rolls 11 and 13 is mounted in cbocks 11a and 13a in thehousing 10. The lower work roll 12 is backed up by a lower back-up roll14 and both are mounted in chocks 12a and 14a movable in the housing 10in the vertical direction. An hydraulic cylinder 16 is mounted beneatheach of the chocks 14a of the lowermost back-up roll 14 and is providedwith a piston 17 bearing against the check 14a of the back-up roll 14.Hydraulic fluid under constant pressure is delivered to the cylinder 16through an hydraulic line 17a from a reservoir 18 through pump 19 and arelief valve 26 which maintains a constant pressure on the cylinder 16.The pump 19 is driven by an electric motor 19a. The desired pressure isregulated by a pressure control 21. When a strip of steel is passedbetween the work rolls 11 and 12, the pressure control is adjusted tothe desired pressure to force the checks 14a of the back-up roll 14upwardly so that back-up roll 14 bears against the work roll 12,pressing the strip between the work rolls 11 and 1.2 at a pressure suchas will perform the desired amount of work to produce a given finish andthe desired workhardening effects. As the strip moves through the workrolls 11 and 12 this constant pressure is maintained between rolls 11and 12 without regard to variations in strip thickness so that all partsof the strip receive the same amount of work, thus eliminating theundesirable unevenness in treatment which results from conventionalscrewdown temper pass or skin pass mills.

In FIGURE 2 I have illustrated a second embodiment of my invention. Inthis embodiment, I show a housing 30 carrying work rolls 31 and 32backed up by back-up rolls 33 and 34. The work rolls 31 and are mountedon opposite sides of a strip pass line 35. The upper work roll 31 andits associated back-up roll 33 are mounted in chocks 31a and 33arespectively in the housing 30. The lower work roll 32 and its back-uproll 34 are mounted in chocks 32a and 34a movable vertically in housing10 below the pass line 35. A pair of vertical hanger arms 36 areconnected to the chock 34a of the back-up roll 34 by means of pivot pins37 which permit movement of the checks with respect to the hanger. Eacharm 36 is fixed to an end of a saddle beam 38 which is raised andlowered by a hydraulic piston 39 in cylinder 40 mounted on housing 34).Hydraulic fluid is introduced into the cylinder 40 by means of a line 41corresponding to line 17 of FIGURE 1. Line 41 receives fiuid underpressure from a pump, relief valve and pressure control assemblyidentical with the assembly of pump 19, relief valve 20 and pressurecontrol 21 of FIG- URE 1. Pressure applied to the piston 39 urges thelower work roll 32 unwardly against the strip 35 under constantpressure.

In FIGURE 3, I have illustrated a preferred form of cylinder and controlfor use in the skin pass mill of FIGURE 1. I have found that whenrolling a single Width and thickness on the mill of this invention anordinary single stage hydraulic cylinder is satisfactory. I have foundthat when various widths of strip are to be rolled in the same mill withdifferent thicknesses, it is desirable to have an hydraulic cylinderhaving several stages of control. I provide a cylinder 50 having mountedtherein an axial piston 51 having an enlarged head 52 in sliding contactwith the wall of the cylinder 50. Surrounding the piston 51 is a secondannular piston 53 having an enlarged head 54 hearing against the wall ofthe cylinder 50 in sliding contact therewith. Surrounding the psiton 53is a cap 55. Hydraulic fluid is supplied from hydraulic pumps 56 and 57to the pistons 52 and 53 through the valves 57a and 58. The arrangementof pistons 51 and 53 is such that fluid may be introduced selectively tothe several pistons. Fluid may be introduced through line 59 from valve57a to chamber 51a beneath only the head 52. In this way, the maximumpressure is applied to piston 51. Alternatively, fluid may be suppliedboth through valve 57a and line 59 to chamber 510 beneath head 52 andthrough line 60 and valve 58 to chamber 53a above the head 52 andbeneath the head 54. This reduces the pressure applied by piston 51 bythe difference between the area of head 54 and the area of the head 52.This provides the minimum pressure applicable by piston 51. As a thirdalternative, fluid may be introduced through line 61 and valve 58 tochamber 550 above head 54 at the same time fluid is introduced throughvalve 57a and line 59 to chamber 51a so that the pressure applied to thehead 52 is counterbalanced by pressure applied to the head 54 on theshoulder 62. In this way, the pressure applied by piston 51 is thedifferential between the pressure on head 52 less the pressure on thearea formed by the shoulder 62. It is thus seen that in the samepressure cylinder 50 there may be achieved three different pressures onthe working piston 51 without any change in the pressure supplied by thepumps 56 and 57. This permits a selection of a variety of pressures tobe applied to the chocks on the bottom roll without any change in thesource of pressure fluid. The volume of fiuid passing to the severalchambers is regulated by volume con trols 63 of conventional design.

In FIGURE 4, I have illustrated a housing 70 having a pair of work rolls71 and 72 on opposite sides of the pass line 73. The upper work roll 71is mounted in movable chocks 74 and is backed up by a crowned backuproll 77 mounted in chocks 76. The lower work roll 72 is mounted inmovable chocks 72a on back-up roll chocks 78a. Chocks 78a are mounted onhydraulic pistons 79 at either end. Hydraulic fluid is supplied to thecylinders 79 by an hydraulic line 80 receiving fluid under constantpressure from an hydraulic pump, relief valve and pressure controlsimilar to pump 19, valve 20 and pressure control 21 of FIGURE 1. Theupper work roll chocks 74 are spaced from the chocks 72a of the lowerwork roll '72 and spaced from the chocks 76 of the back-up roll 77.Hydraulic cylinders 81 are inserted between the chocks 74 and the chocks76 of the upper work roll and the upper back-up roll. Hydrauliccylinders 82 are mounted between the chocks 74 of the upper work rolland the chocks 72a of the lower work roll. Hydraulic cylinders 83 aremounted between chocks 72a and 78a of the lower work roll and lowerback-up roll. Hydraulic fluid is delivered to the cylinders 81, E2 and83 through conventional control valves from a source of hydraulicpressure (not shown). By applying pressure to one of the h,drauliccylinders 81, 82 and 83, the

work roll 71 can be forced toward or away from the back-up roll 77 so asto control its contour by bending the work roll around the crown of theback-up roll. In this way, the work roll 71 can be made to take adesired contour to follow a given strip surface contour. The lower workroll 72 could be similarly provided with a crowned back-up roll (as inFIGURE 1) and hydraulic cylinders similar to cylinders 81 placed betweenthe chocks 72a of the lower work roll and the chocks of its back-up rollso as to cause it to take a given desired contour in the same manner asdescribed for upper work roll 71.

In FIGURE 5, I have illustrated in exaggerated front elevation a pair ofcrowned work rolls and 101, journaled at opposite ends in chocks 102aand b and 103a and b in a housing shown in phantom. The work rolls 100and 101 are backed up by back-up rolls 104 and 105 journaledrespectively in chocks 106a and b and 107a and b in the usual manner. Apair of hydraulic cylinders 108 and 109 are placed between chocks 102aand 106a and 1021; and 1061) respectively and a second pair of hydrauliccylinders 110 and 111 are placed between chocks 103a and 107a and 1015band 107']; respectively. Hydraulic fluid is delivered equally to thecylinders 108, 109, 110 and 111 to cause the work rolls 100 and 101 tobend about a strip passing between them as a fulcrum. The relativeresults of such bending on the strip are schematically illustrated inFIGURES 6A and 613. It is clear from these figures that with a singleset of crowned work rolls it is possible to roll strip which would haverequired many different sets of work rolls with the corresponding manyroll changes. The advantages in capital costs, labor expense and losttime in the mill are obvious.

While I have illustrated certain preferred embodiments of my invention,it will be understood that this invention may be otherwise embodiedwithin the scope of the following claims.

I claim:

1. A rolling mill comprising a housing, a pair of convex work rolls inthe housing on opposite sides of a pass line each having a largerdiameter at the middle than at the ends, said work rolls being adaptedto receive strip therebetween and exert a Working force transversely tothe path thereof, journals for each end of said work rolls, a back-uproll journaled in the housing adjacent each work roll and bearing onsaid adjacent work roll, and pressure means at the ends of said workrolls acting on and moving the journals of said work rolls transverselyto the path of the strip to cause the ends of said work rolls to movetoward each other so as to cause the middle thereof to engage a stripbeing rolled as a fulcrum and to bend said work rolls to decrease theconvexity of said rolls to provide a desired strip contour.

2. A rolling mill as claimed in claim 1 wherein additional pressuremeans are provided between the work roll journals selectively urgingsaid journals apart.

3. A skin pass and temper rolling mill comprising a housing, a pair ofconvex work rolls in the housing on opposite sides or" a pass line eachhaving a larger diameter at the middle than at the ends, said work rollsbeing adapted to receive strip therebetween and exert a working forcetransversely to the path thereof, journals for each end of said workrolls, a back-up roll journaled in the housing adjacent each work rolland bearing on said adjacent work roll, pressure means at the ends ofsaid work rolls acting on and moving the journals of said work rollstransversely to the path of the strip to cause the ends of said workrolls to move toward each other so as to cause the middle thereof toengage a strip being rolled as a fulcrum and to bend said work rolls todecrease the convexity of said rolls to provide a desired strip contour,and constant pressure means acting on the ournals of a back-up rollurging it and the adjacent work roll yieldably toward the pass linewhereby to exert a selected substantially constant working pressure on astrip passing between the work rolls.

4. A skin pass and temper rolling mill as claimed in claim 3 havingadditional pressure means between the Work roll journals selectivelyurging said journals apart.

References Cited in the file of this patent UNITED STATES PATENTS561,078 Menne Apr. 20, 1897 m 6 Tyler Dec. 23, 1941 Pauls Nov. 4, 1947Goulding Sept. 23, 1952 Wellman Mar. 30, 1954 FOREIGN PATENTS GermanyJune 23, 1936 France Nov. 15, 1950 Great Britain July 14, 1937 GreatBritain Sept. 28, 1955

